In the first-ever study, the two researchers examined how effective Ontario-grown onions are at killing breast and colon cancer cells. They discovered the Ruby Ring onion variety came out on top. Onions as a superfood are still not well known. But they contain one of the highest concentrations of quercetin, a type of flavonoid, and Ontario onions boast particularly high levels of the compound compared to onions grown in other parts of the world.

Published recently in Food Research International, the Guelph study revealed that the red onion also has high amounts of anthocyanin, which enriches the scavenging properties of quercetin molecules, making this variety more effective at killing cancer cells.